Candida albicans is a serious opportunistic pathogen for which adequate antibiotic therapy has not been developed. Candida infections frequently complicate important cytotoxic, immunosuppressive, corticosteroid and broad spectrum antibiotic therapy; this is especially true in the therapy of cancer patients. This research program is designed to elucidate the mechanism whereby athymic nude mice are resistant to candidiasis and even more important, why restoration of thymic function abrogates their immunity to candidiasis. Macrophage and PMN function, B-cell activation of macrophage by C. albicans or gram-negative gut flora and antibody-dependent B-cell mediated candida killing, will be investigated to try to explain this unusual finding of resistance to candidiasis. The susceptibility of nude mice to mucocutaneous candidiasis will also be investigated and its usefulness as a model for therapy (cellular or antifungal) will be assessed. The ultimate goal of this program is to achieve a more basic understanding of the factors that are important in the development of acquired resistance to C. albicans.